We have developed and characterized a conventional antiserum against a UDP-galactose:N-acetylglucosamine galactosyltransferase (GT). This antiserum is cross-reactive with GT from several mammalian species including rat, mouse, dog and humans. Using this antiserum we have directly demonstrated the cell surface localization of GT in a variety of different cell types. Using this highly specific immunological probe for GT we will continue in our efforts to: (1)\chemically characterize the cell surface GT on tissue culture cells by a combination of immunopurification and structural analysis; and (2)\to determine, by blocking experiments and monovalent antibody, if this cell surface GT is functionally involved in intercellular adhesion. Two tissue culture systems are under investigation: (1)\a human lung-derived tissue culture line in which cells form a free-floating, three-dimensional multicellular aggregate; and (2)\the mouse embryonal carcinoma F9 cell line for which there is evidence that intercellular adhesion is mediated by a cell surface GT and a poly(N)-acetyllactosamine glycoconjugate.